HR: 16:20h
AN: B44A-02 INVITED    [Abstracts]
TI: Results from a Long-term Litter Decomposition Experiment in Canadian Forests and Their Use in Soil Carbon Model Verification and Development.
AU: * Trofymow, J A
EM: ttrofymow@pfc.forestry.ca
AF: Natural Resources, Canadian Forest Service, 506 Burnside Rd. W., Victoria, BC V8Z 1M5, Canada
AU: Smyth, C
AF: Natural Resources, Canadian Forest Service, 506 Burnside Rd. W., Victoria, BC V8Z 1M5, Canada
AU: Moore, T
AF: Dept. Geography, McGill University, Montreal, QC H3A 2K6, Canada
AU: Prescott, C
AF: Dept. Forest Science, Univ. British Columbia, Vancouver, BC V6T 1Z4, Canada
AU: Titus, B
AF: Natural Resources, Canadian Forest Service, 506 Burnside Rd. W., Victoria, BC V8Z 1M5, Canada
AU: Siltanen, M
AF: Natural Resources, Canadian Forest Service, 5320 122 St., Edmonton, AB T6H 3S5, Canada
AU: Visser, S
AF: Dept. Biological Sciences, Univ. Calgary, Calgary, AB T2N 1N4, Canada
AU: Preston, C
AF: Natural Resources, Canadian Forest Service, 506 Burnside Rd. W., Victoria, BC V8Z 1M5, Canada
AU: Nault, J
AF: Natural Resources, Canadian Forest Service, 506 Burnside Rd. W., Victoria, BC V8Z 1M5, Canada
AU: Nault, J
AF: Faculte' de Foresterie et a` de Geomatique, Univ. Laval, Quebec City, QC G1K 7P4, Canada
AU: Camire', C
AF: Faculte' de Foresterie et a` de Geomatique, Univ. Laval, Quebec City, QC G1K 7P4, Canada
AU: Fyles, J
AF: MacDonald College, McGill University, Ste Anne de Bellevue, QC H9X 1C0, Canada
AU: Kozak, L
AF: Agriculture Agri-Food Canada, CLBRR/LRD, Univ. Saskatchewan, Saskatoon, SK S7N 5A8, Canada
AU: Kranabetter, M
AF: British Columbia Ministry of Forests, Bag 600, Smithers, BC V0J 2N0, Canada
AU: Kutny, L
AF: Inuvik Research Centre, P.O. Box 1430, Inuvik, NW X0EOTO, Canada
AU: Morrison, I
AF: Natural Resources, Canadian Forest Service, 1219 Queen St. East, Sault Ste. Marie, ON P6A 5M7, Canada
AU: Smith, S
AF: Agriculture Agri-Food Canada, Highway 97, Summerland, BC V0H 1Z0, Canada
AU: Wein, R
AF: Faculty Agriculture and Forestry, Univ. Alberta, Edmonton, AB T6G 2P5, Canada
AU: White, D
AF: Forest Management Branch, Energy, Mines and Resources, 345 300 Main St., Whitehorse, YK Y1A 2B5, Canada
AB: Climate and substrate quality have been shown to be key determinants of rates of litter decomposition, though other site factors can be important under certain conditions. The Canadian Intersite Decomposition Experiment (CIDET) was established in 1992 with the objective of providing data on the long-term rates of litter decomposition and nutrient mineralization for a range of forested ecoclimatic regions in Canada. Such data were needed to help verify the Carbon Budget Model - Canadian Forest Sector (CBM-CFS) used for national C accounting, as well as aid in the development of other soil C models. CIDET examined the annual decay, over a 12-year period from 1993 to 2004, of 10 standard foliar litters and 2 wood substrates at 18 forested upland and 3 wetland sites ranging from the cool temperate to subarctic regions. On a subset of sites and litter types, changes in litter C chemistry over time were also determined. Over the first 6 years, C/N ratio and iron increased, NMR showed an overall decline in O-alkyl C (carbohydrates) and increase in alkyl, aromatic, phenolic, and carboxyl C. Proximate analysis showed the acid unhydrolyzable residue (AUR) increases, but true lignin does not accumulate, in contrast to the conceptual ligno-cellulose model of decomposition. Overall litter decay during first phase of decomposition was related to initial litter quality (AUR and water soluble extract), winter precipitation, but not temperature. Decay rate "k" during second phase was related to temperature, initial litter quality (AUR and AUR/N), summer precipitation, but not soil N. In most cases decay had approached an asymptote before end of experiment, although decay rates during this semistable phase were low and difficult to quantify. However, the asymptotes were related to temperature suggesting decay in this phase is temperature dependant. Asymptotes were also related to summer precipitation and forest floor pH and C/N ratio. Comparisons of CIDET 12 year C mass remaining data with CBM-CFS3, showed default model predictions of C remaining were generally too low. Predicted base decay rate was higher than observed for most litter types but the default Q10 value was within the range of observed values. Model optimization to the data reduced absolute error by half. Other climate or site variables that could be used to improve the fit of CBM-CFS3 and fit of CIDET data with other soil C models will be discussed.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0434 Data sets
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting